Blood pressure measurements are one of the most commonly performed medical tests. Blood pressure measurements are typically mad by snugly wrapping a blood pressure cuff around the arm of a patient and fastening it in place. The cuff is then connected to a manometer or automatic blood pressure monitor. Blood pressure measurements may also be made by placing a blood pressure cuff around other limbs, such as a patient's thigh.
Blood pressure cuffs typically consist of a flexible, non-resilient casing having an internal pocket. The pocket normally contains a flexible, air-impermeable bladder. The casing also includes some type of locking device, such as VELCRO.TM. can be used to fasten the casing around the arm of the patient. Some newer blood pressure cuffs utilize a casing fabricated from an air permeable material, and they have an internal bladder thus making a separate bladder contained within an internal pocket unnecessary.
Once the cuff has been fastened around the arm of the patient, its bladder is inflated to occlude the brachial artery beneath the cuff. The pressure in the cuff is then gradually descreased, and the pressure at which blood begins to flow through the brachial artery at systole and diastole is noted to provide a reading of the patient's blood pressure.
While conventional blood pressure cuffs are satisfactory for most uses, they nevertheless suffer some limitations under various conditions. For example, it normally requires two hands to properly position and then snug a blood pressure cuff around the arm of a patient. It is therefore difficult, if not impossible, for some patients to take their own blood pressure, particulary where the patient's mobility is impaired. This disadvantage is becoming increasingly important in view of the increased use of automatic blood pressure monitoring in which blood pressure measurements can be made without the assistance of skilled medical practitioners.
In order to make it easier for blood pressure cuffs to be properly installed, particularly where they are self-installed, various type of automatic cuff installing and fastening devices have been developed. For example, one type of blood pressure cuff uses a small motor to place the cuff around the arm of a patient and an automatic latch to fasten the cuff in place. However, such automatic blood pressure cuffs are expensive and do not always work satisfactorily.
One conventional blood pressure cuff that can be automatically installed around the arm of a patient is available from Life Medical. The Life Medical cuff consists of a single resilient bladder lining the inner wall of a rigid cylindrical tube. A patients' arm is inserted into the tube and bladder until the tube and bladder are positioned over the brachial artery. The bladder is then inflated to occlude the brachial artery, and the pressure is then gradually reduced until the measurement has been completed.
One advantage of the Life Medical cuff is that it is self-snugging. It is not necessary for the cuff to be snugly placed around the arm of a patient because pressurization of the bladder performs the dual function of snugging the cuff against the patient's arm and occluding the brachial artery.
While the Life Medical cuff has the advantage of being self snugging, it is inherently incapable of performing accurate measurements because its bladder cannot be sized to perform the snugging function and still conform to the American National Standard ("ANS"). The ANS is the result of tests conducted to determine the optimum bladder size for obtaining accurate blood pressure measurement. The ANS specifies that a blood pressure cuff bladder should be 80 percent of the circumference of the arm on which it is installed. However, it is not possible for a blood presssure bladder extending all the way around an arm to be 80 percent of the circumference of the arm.